Electro-thermal chemical (ETC) gun systems have been developed in response to a need for improved medium and large caliber gun performance. Typically, an ETC ammunition round has an igniter assembly. The igniter assembly serves to generate a high-energy plasma from electrical energy supplied to the igniter, and to inject the plasma into a mass of chemical propellant, which is then ignited by the high-temperature plasma. The very high energy and temperature of the plasma enables the use of multi-layer and higher density chemical propellants. Such propellants, although harder to ignite, enable a stronger and more lengthy useful pressure pulse to the projectile, thereby improving gun system performance. One example of such a propellant system is disclosed in U.S. Pat. No. 6,167,810, which is assigned to the owner of the present invention, and which is hereby fully incorporated herein by reference. In addition, the plasma energy itself may serve to provide an additional accelerating force to the projectile, thereby improving gun performance.
Examples of plasma igniter apparatus for ETC gun systems are disclosed in U.S. Pat. Nos. 5,231,242, 5,287,791, 5,503,081, 5,767,439, 5,444,208, 5,830,377, all assigned to the owner of the present invention, and each of which is hereby fully incorporated by reference herein. In addition, further examples of an ETC plasma igniter are disclosed in co-pending U.S. patent application Ser. No. 09/767,542, assigned to the owner of the present invention, and fully incorporated herein by reference.
Generally, it is desirable that an ETC igniter apparatus supply about 100 kJ or more of plasma energy to the mass of chemical propellant in an ETC cartridge. As a consequence, it is necessary to supply a slightly greater amount of electrical energy to the igniter. Moreover, for effective plasma formation, the electrical energy must be supplied over a time period measured in milliseconds. As a result, very high electrical currents at very high voltages are necessary to transfer the energy in the requisite amount of time. Currents over 50 kA or more are often necessary.
Transmission of electrical power at very high current levels presents unique challenges in the design of conductors and connection equipment. Excessive resistance in the current path will cause very rapid and destructive heating effects. In addition, strong magnetic fields may be created which can cause catastrophic failure of conductors and connectors. Moreover, connection interfaces between components in the conductive path may be prone to arcing if contaminated or if insufficient force holds the components together. As a result, it is necessary to provide a strong biasing force to press together components in the current path. This biasing force may reach levels over 1000 pounds of force, imposing high stress loads on components.
Transmission of electrical power at high currents to a plasma igniter in an ETC gun application presents even greater challenges due to the extreme physical loading characteristics of the application. The breech assembly of a typical 120 mm ETC gun may be subjected to a load of more than 2,000,000 pounds upon firing, resulting in instantaneous stress loads of more than 100,000 p.s.i. in certain components. In addition, the gun and breech assembly must be designed to permit recoil. Thus, power cables must be sufficiently flexible to enable recoil, which may exceed two feet in some cases.
Specialized coaxial cables and connectors have been developed in response to the above challenges. For example, a high energy flexible coaxial cable and connector suitable for use in ETC gun applications are disclosed in U.S. Pat. No. 5,656,796, assigned to the owner of the present invention, and fully incorporated herein by reference. In addition, embodiments of another high energy power connector usable in ETC gun applications are disclosed in U.S. Pat. No. 5,220,126, assigned to the owner of the present invention, also fully incorporated herein by reference.
Past solutions, although generally successful in conveying power to an ETC gun plasma igniter while overcoming some of the electrical and physical problems described above, have not been fully suitable for practical use in a battlefield setting for a variety of reasons. The current return path in prior solutions typically leads through portions of the gun that may be exposed to human contact. Due to the high voltages and current present in the return path, such exposed portions can present an extreme life safety hazard to personnel operating the gun, particularly where the gun may be located in a confined space such as a tank turret. Moreover, sensitive electronic devices, which may be used for communication, fire control, or other purposes, are subject to damage from stray currents or strong magnetic fields generated by the current.
In addition, the power connection in some prior art devices relies on permanent deformation of the connection components or on cumbersome and complicated connectors in order to achieve sufficient connection force to avoid arcing. These methods and devices are generally unsuitable for a battlefield device which must be capable of repeated, reliable, and rapid connection and disconnection so that a relatively high rate of fire may be achieved.
What is still needed is a high-energy power connection apparatus, especially adapted for use in a battlefield setting, that is suitable for connecting an ETC igniter apparatus in an ETC gun with a high-energy power source.